1. Field of the Invention
The present invention relates to corrosion inhibiting compositions and methods for inhibiting the corrosion of metal surfaces by corrosive aqueous fluids.
2. Description of the Prior Art
Subterranean hydrocarbon containing formations penetrated by well bores are often treated with aqueous acids to stimulate the production of hydrocarbons therefrom. One such treatment generally referred to as "acidizing" involves the introduction of an aqueous acid solution into a subterranean formation under pressure so that the acid solution flows through the pore spaces of the formation. The acid reacts with acid soluble materials contained in the formation thereby increasing the size of the pore spaces and increasing the permeability of the formation. Another production stimulation treatment known as "fracture-acidizing" involves the formation of one or more fractures in the formation and the introduction of an aqueous acid solution into the fractures to etch the fracture faces whereby channels are formed therein when the fractures close. The acid also enlarges the pore spaces in the fracture faces and in the formation.
While acidizing and fracture-acidizing well stimulation treatments have been performed successfully for many years, a continuous problem which accompanies the treatments is the corrosion of metal surfaces in pumps, tubular goods and equipment used to introduce aqueous acid solutions into the subterranean formations to be treated. The expense associated with repairing or replacing corrosion damaged tubular goods and equipment can be very high. The corrosion of tubular goods and down-hole equipment is increased by the elevated temperatures encountered in deep formations, and the corrosion results in at least the partial neutralization of the acid before it reacts with acid-soluble materials in the formations.
Aqueous acid solutions are also utilized in a variety of other industrial applications to contact and react with acid soluble materials. In such applications, metal surfaces are necessarily also contacted with the acid and any corrosion of the metal surfaces is highly undesirable. In addition, other corrosive fluids such as aqueous alkaline solutions, heavy brines, petroleum streams containing acidic materials and the like are commonly transported through and corrode metal surfaces in tubular goods, pipelines and pumping equipment.
A variety of metal corrosion inhibiting compositions and formulations which can be added to aqueous corrosive fluids have been developed and used heretofore. While such compositions and formulations have achieved varying degrees of success in preventing corrosion of metal surfaces, there is a continuing need for improved metal corrosion inhibiting compositions which are effective when combined with aqueous corrosive fluids of the types described above and which provide greater and more reliable corrosion inhibition than has heretofore been possible.